DESCRIPTION Abstract: The role of vitamin D in bone metabolism is well established, but recent epidemiologic and basic science studies suggest that vitamin D related pathways are involved in the determination of pulmonary function, risk of infection, and respiratory health, all factors influencing morbidity and mortality in chronic SCI. These observations regarding vitamin D are highly significant as vitamin D deficiency and insufficiency is common in chronic spinal cord injury. Previous research conducted at VA Boston in persons with chronic SCI has demonstrated that longitudinal decline in pulmonary function and chest illness risk are not attributable to level and severity of injury, but to other potentially modifiable factors. The VA Boston SCI research program has conducted epidemiologic studies focused on identifying factors responsible for pulmonary function decline and pulmonary-related illness in chronic SCI. In a cohort of 330 persons with chronic SCI, it is proposed to longitudinally assess the relationship between vitamin D levels with pulmonary function and the risk of future chest illness. Understanding these adverse effects of lower vitamin D levels is particularly important in SCI because of the increased risk of pulmonary-related diseases and infection. Our approach is efficient because it will take advantage of a large SCI cohort enrolled in an ongoing longitudinal health study. The demonstration of an association between pulmonary function decline and an increased risk of chest illness with lower levels of vitamin D would result in a clinical trial assessing the potential benefits of vitamin D supplementation that would potentially identify an approach to disease prevention in SCI.